Oxidation of acrolein to



Reissueii May 18, 1948 OXIDATION OF ACROLEIN T ACRYLIC ACID Hanna Peter Staudinger, Ewell, and Karl Heinrich Walter Tuerck, Banstead, England, asslgn- V ore to The Distillers Company Limited, Edinburgh, Scotland, at British company No Drawing.

Original No. 2,341,339, dated February 8, 1944, Serial No. 411,758, September 20,

1941. Application for reissue February 12,

1946, Serial No. 647,186. In Great Britain September 21, 1940 4 Claims. 1

This invention is for improvements in or relating to the oxidation of acrolein to acrylic acid.

Several processes for oxidising acrolein to acrylic acid have been described in theliterature, but all these processes have suilered from the factthat the oxidation, as hitherto practised, has been slow and polymerisation of both the acrolein and the acrylic acid produced by the process takes place at a rapid rate. This poly: merisation is thought to be due either to the prolonged action oi! the oxygen itself, or more probably to the action of per compounds formed as intermediate compounds during the reaction.

According to the present invention, the oxidation of acrolein is carried out by reaction with molecular oxygen, that is oxygen itself, or gases containing oxygen, in the presence of the acidic compounds of vanadium such as vanadic acid. The catalyst is prelerably freshly prepared from the corresponding salts by hydrolysis or by the action of acids.

The use of vanadic acid as catalyst not only considerably reduces the reaction time, but also permits the use oi lower temperatures than has been possible hitherto with a consequent diminution in the tendency to polymerisation. The tempenature should preferably not be allowed to exceed 45 C. during the oxidationand generally speaking-a temperature of 20-30 C. will beiound to give most satisfactory results. Though the solution contains a considerable amount of peracid and peroxide the monomeric acrylic acid is obtained in very good yields. 1

, The oxidation may be carried out in the presence of solvents preferably water-miscible solvents such as the lower organic acids, e. g., acetic acid or acrylic acid, alcohols or -ketones. It is also possible to carry out the oxidation in the presence of water and a satisfactory method of operation is to use the catalyst, e. g., vanadic acid, in the form oi! its aqueous solution or suspension. It is possible according to the process of the present invention to carry the-oxidation substantially to completion, without undue polymerisation taking place.

We have round that polymerisation oi the unsaturated acid produced by the process can be prevented during the recovery or the product by the use 0! substances which decompose the formed peroxides which promote polymerisation. An example oi such a substance is. sulphur dioxide, As the rate of oxidation is high the process may be carried out in a continuous manner. also possible to carry out the oxidation under such condition that the acid anhydride is termed.

. The oxidation is normally carried out at ordinary pressure but, if desirable, increased pressure may be treated with acetylene in the presence of suitable catalysts, 'such as mercuric oxide, and the acrylic acid converted directly into vinyl acrylate. Alternatively, the reaction mixture may be treated with an'alcohol and an esterification catalyst. Yet another method is to cause esterification of the acrylic acid to take place simultaneously with the oxidation by carrying out the oxidation in the presence of an alcohol. If in the latter process the temperature is maintained at a low level. the formation of acroiein acetal can be substantially avoided.

The process is applicable not only to the oxidation or acrolein but also to the oxidation oi achloro-acrolein.

The following examples illustrate the manner in which the invention is carried into effect in the production of acrylic acid.

Example 1 Oxygen was introduced into '40 grams of acrolein dissolved in 50 grams of acetic acid containing 4 cc. of a 1% solution oi! freshly prepared vanadic acid in water. The oxygen is introduced 32 grams of acrolein were dissolved in 40 cc.-

oi' acetoneand 5 cc. of acetic acid. The solution was then treated with oxygen in the presence of 2 cc. of a 1% aqueous vanadic' acid solution at 30 C. Alter five hours 64% of the acrolein was oxidised to acrylic acid while 30% remained lachanged. No polymerisation was observed.

Example 3 A mixture containing 50 grams absolute alcohol, 43 grams acrolein, 5 cc. acetic acid and i 2 cc. of a 1% aqueous vanadic acid solution was treated with oxygen at about 30 C. After a short induction period the absorption of oxygen increased so markedly that intensive cooling was necessary. The reactin product contained 32% acrylic acid and 62% of ethyl acrylate. No polymerisation was observed.

Example 4 The voluminous precipitate obtained by heating sodium-vanadate with acetic acid was redispersed in acetic acid and added to an acetic acid solution containing 40% by weight of acrolein. This solution was oxidised at 10 C. by

passing in oxygen under a pressure of 1300 mm. Hg. The yield of monomeric acrylic acid was 93.2%, 87.0% oi the acrolein initially present having undergone reaction.

Example 5 A 40% solution of acrolein in xylene was oxidised for 5 hours at 32 C. in the presence of a catalyst, made by heating solid vanadium pentoxide which is dispersed in acetic acid with small amounts of hydrogen peroxideI so that the solid vanadium pentoxide partially dissolves. By adding the calculated amount of acetic anhydride the water in the catalyst solution is removed. The yield of monomeric acrylic acid was 92%.

What we claim is:

4 aliprocessaccordingtoclaimlwhereinthe catalystisn mredinsitubyreactionbetween vanadium pentoxlde, acetic acid and hydrogen peroxide.

4. A process for the manufacture of acrylic acid which comprises treating acrolein in solu-- tion in a water-soluble carboxylic acid havin no more than three carbon atoms with an oxygencontaining gas in the presence of a catalyst comprising an. aqueous solution of vanadic acid at a temperature not exceeding 45 reaction product containing monomeric acrylic acid and peroxidic compounds. HANNS PETER. BTAUDINGER. KARL HEINRICH WALTER TUERCK.

REFERENCES CITED The following references are oi record in the flle of this patent:

1. A process for the manufacture of acrylic acid comprising treating acroiein in presence oi acetic acid with an oxygen-containing gas in the presence of a catalyst comprising an aqueous solution of vanadic acid at a temperature not exceeding 45 C. to produce a. reaction product containing monomeric acrylic acid and peroxidic compounds.

2. A process according to claim 1 wherein the 1 reaction is carried out at a temperature of 20 to 30 C. and in presence 01' ganic solvent.

9. water-miscible or- UNITED s'ra'ms iA'l'ENT-S Number Name Date 1,081,959 Gi'lmstein Dec. 23, 1913 2,153,406 Bauer Apr. 4, 1939 2,183,325 Staudinger Dec. 12, 1939 2,210,469 Staudlllger A113. 6, 1940 2,212,900 Groll et a1. Aug. 27, 1940 FOREIGN PATENTS Number Country Date 369,963 Great Britain Mar. 17, 1932 OTHER REFERENCES Mellor, "Comprehensive Treatise on Inorg. and Theoretical Chemistry," vol. 9 (Longman's et aL, 1929) pages 743-755. and 794-795.

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